<!DOCTYPE html>
<html>
<head>
<script type="text/javascript">

function boom()
{
  window.addEventListener("DOMSubtreeModified", function(){}, false);

  var span = document.createElement("span");
  document.body.appendChild(span);
}

</script>

<style type="text/css">

span:before { content: '0'; }
span:after { content: '1'; }

</style>
</head>

<body onload="boom();"></body>
</html>
